This study will investigate the safety of sertraline (Zoloft) in patients with recent myocardial infarction who are experiencing an episode of major depression. Many investigations have shown that elevated levels of symptoms of depression are associated with an increased risk of death due to cardiovascular disease. Recently, major depressive disorder occurring in the first few weeks after myocardial infarction (MI) was shown to be associated with a four-fold increase in the risk of death over the subsequent 6-18 months, even after adjustment for other risk factors. Although the efficacy and safety of serotonin reuptake inhibitor antidepressants have been established in trials with over 10,000 patients, patients with unstable coronary artery disease or recent MI have generally been excluded from these studies. This study will be a multi-site randomized double-blind parallel-group study comparing sertraline to placebo treatment in patients with clinically diagnosed depression following acute myocardial infarction.